Intuition

To summarize ranges in a sorted array, we can identify segments of consecutive numbers. Whenever a gap occurs between two numbers, it marks the end of the current range
https://leetcode.com/problems/summary-ranges/description/

Approach

We iterate through the array while keeping track of the start of the current range using a variable s.By appending float('inf') to the list, we ensure the final range is processed without requiring additional checks after the loop

At each step, we check if nums[i] - nums[i-1] > 1, which means the consecutive sequence has ended

We then:

• Record the range from s to nums[i-1]
• Update s to start a new range from nums[i]

If the start and end of the range are the same, we store it as a single number. Otherwise, we use the "start->end" format

Complexity

• Time complexity:

$O(n)$ — We go through the list once

• Space complexity:[[]()]()

$O(n)$ — for storing the resulting list of summary strings

Code

class Solution:
    def summaryRanges(self, nums: List[int]) -> List[str]:
        nums.append(float('inf'))
        a=[]
        s=nums[0]
        for i in range(1,len(nums)):
            if nums[i]-nums[i-1]>1:
                e=nums[i-1]
                if s==e: itv=str(s)
                else: itv=str(s)+"->"+str(e)
                a.append(itv)
                s=nums[i]
        return a